The surfacing welding is the common repairing technology and an effective way for the repair of local damage occurs at the magnesium equipment surfaces. The effects of varying contents of the yttrium on the dry sliding wear behavior of surfacing AZ91 magnesium alloys were investigated in this work. The results demonstrated that the surfacing AZ91 alloy without yttrium addition exhibited poor wear resistance, due to the massive intermetallic β- Mg17Al12 phases. With the addition of yttrium, wear resistance was improved resulting from the decrease of size and quantity of the β phase, which reduced the alloy hardness and decreased the subsurface metal deformation degree caused by friction. Three primary wear mechanisms were observed: abrasion, oxidation and delamination.